The Second Coming of Ultrasound


At the Sunnybrook Institute in Toronto, doctors have begun using focused ultrasound, delivered through helmet-like devices such as this, to loosen the blood-brain barrier, making it possible to deliver life-saving drugs.

Before Pierre Curie met the chemist Marie Sklodowska; before they married and she took his name; before he abandoned his physics work and moved into her laboratory on Rue Lhomond where they would discover the radioactive elements polonium and radium, Curie discovered something called piezoelectricity. Some materials, he found—like quartz and certain kinds of salts and ceramics—build up an electric charge when you squeeze them. Sure, it’s no nuclear power. But thanks to piezoelectricity, US troops could locate enemy submarinesduring World War I. Thousands of expectant parents could see their baby’s face for the first time. And one day soon, it may be how doctors cure disease.

Ultrasound, as you may have figured out by now, runs on piezoelectricity. Applying voltage to a piezoelectric crystal makes it vibrate, sending out a sound wave. When the echo that bounces back is converted into electrical signals, you get an image of, say, a fetus, or a submarine. But in the last few years, the lo-fi tech has reinvented itself in some weird new ways.

Researchers are fitting people’s heads with ultrasound-emitting helmets to treat tremors and Alzheimer’s. They’re using it to remotely activate cancer-fighting immune cells. Startups are designing swallowable capsules and ultrasonically vibrating enemas to shoot drugs into the bloodstream. One company is even using the shockwaves to heal wounds—stuff Curie never could have even imagined.

So how did this 100-year-old technology learn some new tricks? With the help of modern-day medical imaging, and lots and lots of bubbles.

Bubbles are what brought Tao Sun from Nanjing, China to California as an exchange student in 2011, and eventually to the Focused Ultrasound Lab at Brigham and Women’s Hospital and Harvard Medical School. The 27-year-old electrical engineering grad student studies a particular kind of bubble—the gas-filled microbubbles that technicians use to bump up contrast in grainy ultrasound images. Passing ultrasonic waves compress the bubbles’ gas cores, resulting in a stronger echo that pops out against tissue. “We’re starting to realize they can be much more versatile,” says Sun. “We can chemically design their shells to alter their physical properties, load them with tissue-seeking markers, even attach drugs to them.”

Nearly two decades ago, scientists discovered that those microbubbles could do something else: They could shake loose the blood-brain barrier. This impassable membrane is why neurological conditions like epilepsy, Alzheimer’s, and Parkinson’s are so hard to treat: 98 percent of drugs simply can’t get to the brain. But if you station a battalion of microbubbles at the barrier and hit them with a focused beam of ultrasound, the tiny orbs begin to oscillate. They grow and grow until they reach the critical size of 8 microns, and then, like some Grey Wizard magic, the blood-brain barrier opens—and for a few hours, any drugs that happen to be in the bloodstream can also slip in. Things like chemo drugs, or anti-seizure medications.

This is both super cool and not a little bit scary. Too much pressure and those bubbles can implode violently, irreversibly damaging the barrier.

That’s where Sun comes in. Last year he developed a device that could listen in on the bubbles and tell how stable they were. If he eavesdropped while playing with the ultrasound input, he could find a sweet spot where the barrier opens andthe bubbles don’t burst. In November, Sun’s team successfully tested the approach in rats and mice, publishing their results inProceedings in the National Academy of Sciences.

“In the longer term we want to make this into something that doesn’t require a super complicated device, something idiot-proof that can be used in any doctor’s office,” says Nathan McDannold, co-author on Sun’s paper and director of the Focused Ultrasound Lab. He discovered ultrasonic blood-brain barrier disruption, along with biomedical physicist Kullervo Hynynen, who is leading the world’s first clinical trial evaluating its usefulness for Alzheimer’s patients at the Sunnybrook Research Institute in Toronto. Current technology requires patients to don special ultrasound helmets and hop in an MRI machine, to ensure the sonic beams go to the right place. For the treatment to gain any widespread traction, it’ll have to become as portable as the ultrasound carts wheeled around hospitals today.

More recently, scientists have realized that the blood-brain barrier isn’t the only tissue that could benefit from ultrasound and microbubbles. The colon, for instance, is pretty terrible at absorbing the most common drugs for treating Crohn’s disease, ulcerative colitis, and other inflammatory bowel diseases. So they’re often delivered via enemas—which, inconveniently, need to be left in for hours.

But if you send ultrasound waves waves through the colon, you could shorten that process to minutes. In 2015, pioneering MIT engineer Robert Langer and then-PhD student Carl Schoellhammer showed that mice treated with mesalamine and one second of ultrasound every day for two weeks were cured of their colitis symptoms. The method also worked to deliver insulin, a far larger molecule, into pigs.

Since then, the duo has continued to develop the technology within a start-up called Suono Bio, which is supported by MIT’s tech accelerator, The Engine. The company intends to submit its tech for FDA approval in humans sometime later this year.

Instead of injecting manufactured microbubbles, Suono Bio uses ultrasound to make them in the wilds of the gut. They act like jets, propelling whatever is in the liquid into nearby tissues. In addition to its backdoor approach, Suono is also working on an ultrasound-emitting capsule that could work in the stomach for things like insulin, which is too fragile to be orally administered (hence all the needle sticks). But Schoellhammer says they have yet to find a limit on the kinds of molecules they can force into the bloodstream using ultrasound.

“We’ve done small molecules, we’ve done biologics, we’ve tried DNA, naked RNA, we’ve even tried Crispr,” he says. “As superficial as it may sound, it all just works.”

Earlier this year, Schoellhammer and his colleagues used ultrasound to deliver a scrap of RNA that was designed to silence production of a protein called tumor necrosis factor in mice with colitis. (And yes, this involved designing 20mm-long ultrasound wands to fit in their rectums). Seven days later, levels of the inflammatory protein had decreased sevenfold and symptoms had dissipated.

Now, without human data, it’s a little premature to say that ultrasound is a cure-all for the delivery problems facing gene therapies using Crispr and RNA silencing. But these early animal studies do offer some insights into how the tech might be used to treat genetic conditions in specific tissues.

Even more intriguing though, is the possibility of using ultrasound to remotely control genetically-engineered cells. That’s what new research led by Peter Yingxiao Wang, a bioengineer at UC San Diego, promises to do. The latest craze in oncology is designing the T-cells of your immune system to better target and kill cancer cells. But so far no one has found a way to go after solid tumors without having the T-cells also attack healthy tissue. Being able to turn on T-cells near a tumor but nowhere else would solve that.

Wang’s team took a big step in that direction last week, publishing a paper that showed how you could convert an ultrasonic signal into a genetic one. The secret? More microbubbles.

This time, they coupled the bubbles to proteins on the surface of a specially designed T-cell. Every time an ultrasonic wave passed by, the bubble would expand and shrink, opening and closing the protein, letting calcium ions flow into the cell. The calcium would eventually trigger the T-cell to make a set of genetically encoded receptors, directing it it to attack the tumor.

“Now we’re working on figuring out the detection piece,” says Wang. “Adding another receptor so that we’ll known when they’ve accumulated at the tumor site, then we’ll use ultrasound to turn them on.”

In his death, Pierre Curie was quickly eclipsed by Marie; she went on to win another Nobel, this time in chemistry. The discovery for which she had become so famous—radiation—would eventually take her life, though it would save the lives of so many cancer patients in the decades to follow. As ultrasound’s second act unfolds, perhaps her husband’s first great discovery will do the same.

This Incredible Virus Attacks Brain Cancer And Actually Boosts Our Immune System


The first therapeutic virus to pass the blood-brain barrier.

A study attempting to show that viruses could be delivered to brain tumours has delivered that and more.

Not only did the virus in question reach its target, it also stimulated the patient’s own immune system – which then also attacked the tumour.

 

Preclinical experiments in mice, followed by window-of-opportunity trials in nine human patients, showed that the naturally occurring virus offers potential for a new type of cancer therapy that could be used alongside other treatments.

The virus they used is one that has previously shown potential for cancer treatment – what is known as an oncolytic virus.

It’s called mammalian orthoreovirus type 3, from the reovirus family, and it has previously been shown to kill tumour cells, but leave healthy cells alone.

Previous experiments have demonstrated this mechanism, but researchers from the University of Leeds are the first to successfully direct it at brain tumours.

This is because, until now, it was thought unlikely that the reovirus would be able to cross the blood-brain barrier, a membrane that protects the brain from pathogens.

“This is the first time it has been shown that a therapeutic virus is able to pass through the brain-blood barrier, and that opens up the possibility this type of immunotherapy could be used to treat more people with aggressive brain cancers,” co-lead author Adel Samson said.

Nine patients were selected to be injected with the virus via a single-dose intravenous drip. All either had brain tumours that had spread to other parts of the body, or fast-growing gliomas – a type of brain tumour that is difficult to treat and has a poor prognosis.

All were scheduled to have their brain tumours surgically removed in a matter of days following the reovirus experiment.

The researchers took samples from their tumours after they had been removed, and compared to the tumours of patients who had had brain surgery, but not the reovirus treatment beforehand.

The researchers found the virus in the tumour samples of the trial patients, clearly showing that the virus has been able to reach the cancer.

But they also found an elevated level of interferons, the proteins that activate our immune system. The team says that these interferons were attracting white blood cells to the site to fight the tumour.

“Our immune systems aren’t very good at ‘seeing’ cancers – partly because cancer cells look like our body’s own cells, and partly because cancers are good at telling immune cells to turn a blind eye. But the immune system is very good at seeing viruses,” said co-lead author Alan Melcher.

“In our study, we were able to show that reovirus could infect cancer cells in the brain. And, importantly, brain tumours infected with reovirus became much more visible to the immune system.”

These findings are already being applied in a clinical trial, where patients are being given the reovirus treatment in addition to chemotherapy and radiotherapy. One patient’s treatment is already underway – he is being given 16 doses of the reovirus to treat his glioblastoma.

The reason he is being given multiple doses is because of the way the virus activates the immune system. This clinical trial will determine how well cancer patients can tolerate the treatment, since the virus creates flu-like side effects, and whether it makes the standard treatments more effective.

“The presence of cancer in the brain dampens the body’s own immune system. The presence of the reovirus counteracts this and stimulates the defence system into action,” said one of the researchers, oncologist Susan Short, who is also leading the clinical trial.

“Our hope is that the additional effect of the virus on enhancing the body’s immune response to the tumour will increase the amount of tumour cells that are killed by the standard treatment, radiotherapy and chemotherapy.”

Ultrasound Opens the Brain to Promising Drugs


The protective sheath surrounding the brain’s blood supply—known as the blood-brain barrier—is a safeguard against nasty germs and toxins. But it also prevents existing drugs that could potentially be used to treat brain cancer or Alzheimer’s disease from reaching the brain. That’s why scientists want to unchain the gates of this barrier. Now a new study shows it’s been done in cancer patients.

The procedure works by first injecting microbubbles into the bloodstream and then using a device implanted near patients’ tumors to send ultrasonic soundwaves into the brain, exciting the bubbles. The physical pressure of the bubbles pushing on the cells temporarily opens the blood-brain barrier, letting an injected drug cross into the brain.

Alexandre Carpentier holds the SonoCloud device, which he has implanted in 15 brain cancer patients.

“People for years have been trying to open the blood-brain barrier,” said Neal Kassell, founder of theFocused Ultrasound Foundation. The device, called SonoCloud, was implanted and used on 15 patients during monthly chemotherapy with no ill effects after six months.

Although this is the first published study using ultrasound to open the blood-brain barrier in humans, it is not the first study to hit the news. In November, a team at the Sunnybrook Health Sciences Centre in Toronto announced the start of a clinical trial to open the blood-brain barrier using ultrasound in a single brain cancer patient. Carpentier’s trial, on the other hand, began in July 2014, and Kassell said the French study “is the first time they’ve shown the safety of repetitively opening the blood-brain barrier in humans.” Both clinical trials are ongoing.

The Sunnybrook trial used a focused ultrasound device, which is good for pinpointing localized cancers. In contrast, SonoCloud emits ultrasound more diffusely, which is useful for glioblastomas that blend into surrounding brain tissue. “It seems a little more aggressive to implant something,” Carpentier said, but the wider-ranging ultrasound opens a larger swath of the blood-brain barrier. This enables chemotherapy drugs to reach cancer cells around the periphery of the main tumor, hopefully reducing the chance that the cancer will grow back.

Magnetic resonance brain scans from one patient indicate that opening the blood-brain barrier with SonoCloud resulted in no further tumor progression.

Carpentier, who invented SonoCloud and founded its parent company, CarThera, says the most surprising part was the patients’ response to the implant. “The patients don’t feel anything when we emit ultrasound,” he says. “And they actually don’t complain about it. It was set up in the protocol to remove it after six months, but patients don’t want to remove it.”

He is now designing the next phase of the clinical trial to determine how much more effective the chemotherapy is with an opened blood-brain barrier. Carpentier says the technology is a “huge opportunity” to improve treatment of many diseases. He is also beginning work on a trial with Alzheimer’s patients, since studies in mice have showed that merely opening the blood-brain barrier with ultrasound helps remove the amyloid-β protein thought to be responsible for Alzheimer’s without using any drugs.

The ultimate goal of ultrasound therapy is “to be able to repetitively and reversibly open the blood-brain barrier in a non-invasive, targeted, and focused manner,” Kassell says. “This is one more step toward that goal.”

Nanorobotic agents open the blood-brain barrier, offering hope for new brain treatments


Confocal micrograph from the brainstem showing a central blood vessel with a compromised blood brain barrier. Glial cells, yellow; neurons, blue; blood vessel contents, red. Confocal micrograph. Credit: MRC Toxicology Unit, Wellcome Images

       

Magnetic nanoparticles can open the blood-brain barrier and deliver molecules directly to the brain, say researchers from the University of Montreal, Polytechnique Montréal, and Centre hospitalier universitaire (CHU) Sainte-Justine. This barrier runs inside almost all vessels in the brain and protects it from elements circulating in the blood that may be toxic to the brain. The research is important as currently 98% of therapeutic molecules are also unable to cross the blood-brain barrier. “The barrier is temporary opened at a desired location for approximately 2 hours by a small elevation of the temperature generated by the nanoparticles when exposed to a radio-frequency field,” explained first author and co-inventor Seyed Nasrollah Tabatabaei. “Our tests revealed that this technique is not associated with any inflammation of the brain. This new result could lead to a breakthrough in the way nanoparticles are used in the treatment and diagnosis of brain diseases,” explained the co-investigator, Hélène Girouard. “At the present time, surgery is the only way to treat patients with brain disorders. Moreover, while surgeons are able to operate to remove certain kinds of tumors, some disorders are located in the brain stem, amongst nerves, making surgery impossible,” added collaborator and senior author Anne-Sophie Carret.

Although the technology was developed using murine models and has not yet been tested in humans, the researchers are confident that future research will enable its use in people. “Building on earlier findings and drawing on the global effort of an interdisciplinary team of researchers, this technology proposes a modern version of the vision described almost 40 years ago in the movie Fantastic Voyage, where a miniature submarine navigated in the vascular network to reach a specific region of the brain,” said principal investigator Sylvain Martel. In earlier research, Martel and his team had managed to manipulate the movement of nanoparticles through the body using the magnetic forces generated by magnetic resonance imaging (MRI) machines.

To open the blood-brain barrier, the magnetic nanoparticles are sent to the surface of the blood-brain barrier at a desired location in the brain. Although it was not the technique used in this study, the placement could be achieved by using the MRI technology described above. Then, the researchers generated a radio-frequency field. The nanoparticles reacted to the radio-frequency field by dissipating heat thereby creating a mechanical stress on the barrier. This allows a temporary and localized opening of the barrier for diffusion of therapeutics into the brain.

The technique is unique in many ways. “The result is quite significant since we showed in previous experiments that the same nanoparticles can also be used to navigate therapeutic agents in the vascular network using a clinical MRI scanner,” Martel remarked.  “Linking the navigation capability with these new results would allow therapeutics to be delivered directly to a specific site of the brain, potentially improving significantly the efficacy of the treatment while avoiding systemic circulation of toxic agents that affect healthy tissues and organs,” Carret added. “While other techniques have been developed for delivering drugs to the blood-brain barrier, they either open it too wide, exposing the brain to great risks, or they are not precise enough, leading to scattering of the drugs and possible unwanted side effect,” Martel said.

Although there are many hurdles to overcome before the technology can be used to treat humans, the research team is optimistic. “Although our current results are only proof of concept, we are on the way to achieving our goal of developing a local drug delivery mechanism that will be able to treat oncologic, psychiatric, neurological and neurodegenerative disorders, amongst others,” Carret concluded.

 

To Sleep, Perchance to Clean.


Study reveals brain ‘takes out the trash’ while we sleep.

In findings that give fresh meaning to the old adage that a good night’s sleep clears the mind, a new study shows that a recently discovered system that flushes waste from the brain is primarily active during sleep. This revelation could transform scientists’ understanding of the biological purpose of sleep and point to new ways to treat neurological disorders.

“This study shows that the brain has different functional states when asleep and when awake,” said Maiken Nedergaard, M.D., D.M.Sc., co-director of the University of Rochester Medical Center (URMC) Center for Translational Neuromedicine and lead author of the article. “In fact, the restorative nature of sleep appears to be the result of the active clearance of the by-products of neural activity that accumulate during wakefulness.”

The study, which was published today in the journal Science, reveals that the brain’s unique method of waste removal – dubbed the glymphatic system – is highly active during sleep, clearing away toxins responsible for Alzheimer’s disease and other neurological disorders. Furthermore, the researchers found that during sleep the brain’s cells reduce in size, allowing waste to be removed more effectively.

Image shows cerebral spinal fluid (in blue) entering the brain via a “plumbing system” that piggybacks on the brain’s blood vessels.

The purpose of sleep is a question that has captivated both philosophers and scientists since the time of the ancient Greeks. When considered from a practical standpoint, sleep is a puzzling biological state. Practically every species of animal from the fruit fly to the right whale is known to sleep in some fashion. But this period of dormancy has significant drawbacks, particularly when predators lurk about. This has led to the observation that if sleep does not perform a vital biological function then it is perhaps one of evolution’s biggest mistakes.

While recent findings have shown that sleep can help store and consolidate memories, these benefits do not appear to outweigh the accompanying vulnerability, leading scientists to speculate that there must be a more essential function to the sleep-wake cycle.

The new findings hinge on the discovery last year by Nedergaard and her colleagues of a previously unknown system of waste removal that is unique to the brain. The system responsible for disposing cellular waste in the rest of the body, the lymphatic system, does not extend to the brain. This is because the brain maintains its own closed “ecosystem” and is protected by a complex system molecular gateways – called the blood-brain barrier – that tightly control what enters and exits the brain.

The brain’s process of clearing waste had long eluded scientists for the simple fact that it could only be observed in the living brain, something that was not possible before the advent of new imaging technologies, namely two-photon microscopy. Using these techniques, researchers were able to observe in mice – whose brains are remarkably similar to humans – what amounts to a plumbing system that piggybacks on the brain’s blood vessels and pumps cerebral spinal fluid (CSF) through the brain’s tissue, flushing waste back into the circulatory system where it eventually makes its way to the general blood circulation system and, ultimately, the liver.

The timely removal of waste from the brain is essential where the unchecked accumulation of toxic proteins such as amyloid-beta can lead to Alzheimer’s disease. In fact, almost every neurodegenerative disease is associated with the accumulation of cellular waste products.

One of the clues hinting that the glymphatic system may be more active during sleep was the fact that the amount of energy consumed by the brain does not decrease dramatically while we sleep. Because pumping CSF demands a great deal of energy, researchers speculated that the process of cleaning may not be compatible with the functions the brain must perform when we are awake and actively processing information.

Through a series of experiments in mice, the researchers observed that the glymphatic system was almost 10-fold more active during sleep and that the sleeping brain removed significantly more amyloid-beta.

“The brain only has limited energy at its disposal and it appears that it must choice between two different functional states – awake and aware or asleep and cleaning up,” said Nedergaard. “You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can’t really do both at the same time.”

Another startling finding was that the cells in the brain “shrink” by 60 percent during sleep. This contraction creates more space between the cells and allows CSF to wash more freely through the brain tissue. In contrast, when awake the brain’s cells are closer together, restricting the flow of CSF.

The researchers observed that a hormone called noradrenaline is less active in sleep. This neurotransmitter is known to be released in bursts when brain needs to become alert, typically in response to fear or other external stimulus. The researchers speculate that noradrenaline may serve as a “master regulator” controlling the contraction and expansion of the brain’s cells during sleep-wake cycles.

“These findings have significant implications for treating ‘dirty brain’ disease like Alzheimer’s,” said Nedergaard. “Understanding precisely how and when the brain activates the glymphatic system and clears waste is a critical first step in efforts to potentially modulate this system and make it work more efficiently.”